Setting up SSL: problem redirection from http to https in prestashop 1.6.0.9

we tried the known steps but it seems that we have problem in prestashop, in fact:

we want to set up a certificate ssl for our website:

www.shoptellme.net which is made with prestashop 1.6.0.9 and is hosted in a VPS (that we control)

our certificate is from commodo

you can verify here that the certificate is well set up in the server:

https://sslanalyzer.comodoca.com/?url=www.shoptellme.net

we give you access to the computer of our ingeneer through team viewer and you speak with him via skype

if ok give us your ID skype